Tuberculoid leprosy represents the immunologically stable, pauci-bacillary form of the disease. It is characterized by a strong cellular response with a weak humoral response from the host. There is typically one large, anesthetic erythematous macule or hypopigmented plaque with a well-defined border and atrophic center that may be found on the face or limbs but usually not on the scalp or in the intertriginous regions. The lesions seen in BT are more abundant and smaller in size with peripheral spread and resolving centers. Thickened nerves and loss of function are commonly seen especially with the greater auricular and superficial peroneal nerves. Patients with mid borderline leprosy present with sharply defined annular plaques. Patients with BL have a varied presentation with multiple, symmetrical macules, papules, and nodules found anywhere on the body. These lesions sometimes appear “punched out” and are hypesthetic. The TT is considered the stable form and appear as sharply defined, reddish-brown plaques. The LL form represents systemic involvement, but in the skin, symmetrical, multiple small macules, plaques with poorly defined borders.

Leprosy causes peripheral neuropathy that affects small nerve fibers that convey temperature, touch, pain, and deep pressure. Lepra reactions occur when there is an acute change in the patient’s immune status. The lepra reactions are divided into Type 1 and Type 2. Type 1 lepra reactions consist of swelling of previous plaques and sudden development of new nodules. This type of reaction can be seen in any form of leprosy but is most common in the borderline leprosy stage. Type 2 lepra reactions are also referred to as erythema nodosum leprosum (ENL) and are characterized by tender pink nodules on the extremities with systemic symptoms that may include fever, arthralgias, neuritic pain, uveitis, and orchitis. This reaction only occurs in BL and LL patients.